The invention firstly relates to a blank for producing dental shaped parts as well as a process for producing this blank. The invention furthermore relates to a process for stabilizing the shape of a monolithic dental shaped part during the production thereof as well as a process for producing monolithic dental shaped parts and the monolithic dental shaped parts themselves.
In recent years, ceramic or all-ceramic dental prostheses have become increasingly important. With this type of dental prostheses, the ceramic material is not only used for veneering metal frameworks, as previously known, but the framework material itself is also made from ceramic. In this way, all-ceramic dental prostheses, for example all-ceramic crowns and all-ceramic bridges, are achieved. In this connection, zirconium dioxide in particular is to be emphasized as ceramic material.
In the case of all-ceramic dental prostheses, the frameworks, but also other dental shaped parts such as veneers, abutments (implant structural parts) or even whole teeth, as a rule are machined, in particular milled, from a ceramic block (blank). Such blanks can in principle consist of (finally-)sintered ceramic material which no longer changes its dimensions during further heat treatment. However, a disadvantage here is that such a material can be mechanically processed only with difficulty because of its hardness.
The use of blanks made of an unsintered or not (finally-)sintered ceramic material has therefore proved advantageous. Such materials can be machined dry and are disclosed for example in WO-A1-2004/086999. These materials are used in conjunction with a CAD/CAM technique, which already takes into account the sintering shrinkage of the material during the final-sintering for the machining of the dental prostheses from the blank.
A process for producing a veneer for a dental prosthesis as well as the dental prosthesis itself are described in US 2010/0248189 A1. A precursor of the veneer is produced from a blank, and this blank or this precursor consists of a porous glass ceramic or a porous glass. The disclosure of this document relates expressly to veneers, i.e. to dental shaped parts which, together with a further part, as a rule together with a framework, form the finished dental prosthesis.
Different materials for preparing blanks are already known for the mentioned intended uses. However, there is a further need for such materials, in particular ones that can be machined, in particular milled, dry, i.e. without cooling lubricants.
Furthermore, as far as the applicant is aware, the problem of preparing a monolithic glass dental prosthesis from a porous glass blank that can be milled dry has not been solved. This is because, among other things, during the sintering step necessary to reduce its porosity, glass tends to flow. However, as a dental shaped part, it thus loses its adaptation to the shape of the prepared tooth stump, which is why monolithic dental prosthesis parts made of glass have not been used commercially until now.